Aesthetics only.

 

All of that plastic backing plate against the engine blocks cooling air from the engine, a S&S Stealth air cleaner with the stock outer cover allows a lot more air to cool the engine and the outer cover serves as rain protection.

 

What's the benefit to doing that vs just trimming the stock housing?

 

A better designed backing plate, and better filter element would be the 2 large items. Just taking that piece off, which is just 1 screw still leaves that big backing plate against the engine blocking cooling airflow.

 

Hoi,

"I don't really want an aftermarket filter housing because I want to be able to ride in the rain."

I have an K&N_RC3680_Airfilter on my bike.
When I bought my motorcycle they said if it rains hard you have to take shelter, so as not to suck water through your filter.
Because I live in Belgium, that is a problem. It rains often and when it rains it really is raining.
Parking the bike outside, and riding it in the heavy rain was a big problem.
So there is a rainsock, but I don't like that.
Better solution: raincap.
I made it myself, and tested it in very heavy rain on the highway and ( cloud-burst ) in villages, the engine runs well, no sputtering.
Parking outside is no longer a problem, the filter remains dry.
Below a link to a 3D drawing.
https://grabcad.com/library/raincapairfilter-ii-1
Below a picture.

 

Looks good!

 

Is it possible to buy one somewhere? I'd love to be able to ride my bike when there is a chance of rain in the forecast.

 

Hoi,
I could not find it, that's why I made it.
I am not a metal worker,
and only have a vise, grinder, hammer, saw, drill and an acetylene torch.
It's not difficult, but it does take time. For me anyway.